An Improved Heat Equation to Model Ductile-to-Brittle Failure Mode Transition at High Strain Rates Using Fully Coupled Thermal-Structural Finite Element Analysis

2014 ◽  
Vol 354 ◽  
pp. 1-23 ◽  
Author(s):  
Ladislav Écsi ◽  
P. Élesztős
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Heat Equation ◽  
Brittle Failure ◽  
High Strain ◽  
Strain Rates ◽  
Mode Transition ◽  
Element Analysis ◽  
Failure Mode Transition ◽  
Fully Coupled

In this paper a universal heat equation for fully coupled thermal structural finite element analysis of deformable solids capable of predicting ductile-to-brittle failure mode transition at high strain rates is presented. In the problem mathematical formulation appropriate strain measures describing the onset and the growth of ductile and total damage and heat generation rate per unit volume to model dissipation-induced heating have been employed, which were extended with the heat equation. The model was implemented into a finite element code utilizing an improved weak form for updated Lagrangian formulation, an extended NoIHKH material model for cyclic plasticity of metals applicable in wide range of strain rates and the Jaumann rate in the form of the Green-Naghdi rate in the co-rotational Cauchy’s stress objective integration. The model verification showed excellent agreement with the modelled experiment at low strain rates. Plastic bending of a cantilever has been studied at higher strain rates. A few selected analysis results are presented and briefly discussed.

An Improved Heat Equation for Fully Coupled Thermal-Structural Finite Element Analysis Using Small Strain Formulation

2014 ◽  
Vol 611 ◽  
pp. 294-303
Author(s):  
Ladislav Écsi ◽  
Pavel Élesztős
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Heat Equation ◽  
Mathematical Formulation ◽  
Model Verification ◽  
Cyclic Plasticity ◽  
Ductile Material ◽  
Element Analysis ◽  
Wide Range ◽  
Fully Coupled

In this paper an improved heat equation for fully coupled thermal structural finite element analysis is presented. In the problem solving process, mathematical formulation appropriate strain measures describing the onset and the growth of ductile and total damage and heat generation rate per unit volume for dissipation-induced heating have been employed. The model was implemented into a finite element code using an improved weak form for fully coupled thermal structural finite element analysis, an extended NoIHKH material model with internal damping for cyclic plasticity of metals capable of modelling ductile material behaviour in wide range of strain rates. A notched aluminium alloy specimen in cyclic tension using 2Hz excitation frequency and linearly increasing amplitude has been studied. The model verification showed excellent agreement with available experiments. A few selected analysis results are presented and briefly discussed.

Research Progress on Finite Element Analysis Methods for Bonded Joints at Different Strain Rates

2014 ◽  
Vol 1049-1050 ◽  
pp. 892-900
Author(s):  
Zhe Min Jia ◽  
Guo Qing Yuan ◽  
David Hui
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Strain Rate ◽  
High Strain ◽  
Strain Rates ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Element Analysis ◽  
Adhesively Bonded Joints ◽  
Analysis Methods

Adhesive bonding is one of the effective ways to reduce the weight of structures. Researchers have done lots of numerical analysis and finite element analysis taking into account of the complex stress state in the bonded area, as well as the stress singularity occurs at the overlap edges with a view to efficiently predict the strength and rigidity of adhesively bonded joints. As they may suffer shock or impact loads in practice which leads to high strain rate in structures, analysis methods for adhesively bonded joints differ from that at quasi-static condition for two reasons: one is the mechanical properties of materials, including adhesives and substrates are different at high strain rates, the other is the additional consideration of elastic wave propagation in solid body. This article summaries several finite element analysis methods for adhesively bonded joints at high strain rate developed by domestic and foreign scholars and corresponding experimental standards for determining required parameters of each analytical method and raised some questions that need for further study.

Prediction of Microstructure During High Temperature Forming of Ti-6Al-4V Alloy

2004 ◽  
Vol 449-452 ◽  
pp. 189-192 ◽  
Author(s):  
You Hwan Lee ◽  
T.J. Shin ◽  
Jong Taek Yeom ◽  
Nho Kwang Park ◽  
S.S. Hong ◽  
...  
Keyword(s):  
Activation Energy ◽  
Finite Element Analysis ◽  
Finite Element ◽  
High Temperature ◽  
Flow Stress ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
Element Analysis ◽  
Strain Data ◽  
Final Microstructure

Prediction of final microstructures after high temperature forming of Ti-6Al-4V alloy was´attempted in this study. Using two typical microstructures, i.e., equiaxed and Widmanstätten microstructures, compression test was carried out up to the strain level of 0.6 at various temperatures (700 ~ 1100°C) and strain rates (10-4 ~ 102/s). From the flow stress-strain data, parameters such as strain rate sensitivity (m) and activation energy (Q) were calculated and used to establish constitutive equations for both microstructures. Then, finite element analysis was performed to predict the final microstructure of the deformed body, which was well accorded with the experimental results.

Sign in / Sign up

Export Citation Format

Share Document